It is known that amorphous magnetically soft alloys exhibit more excellent characteristics than crystal materials in respect of corrosion resistance, wear resistance, strength, magnetic permeability, etc. These alloys are used as magnetic materials for various electric or electronic devices.
The amorphous magnetically soft alloy is generally in the form of a thin strip, thin wire or powder because of the reasons involved in the quenching process for assuring the amorphous state. Accordingly when members of specified shape are to be produced with use of such an alloy in the form of a thin strip or wire, the alloy is first pulverized into a powder and then pressed at a predetermined temperature into bodies of the specified shape.
The powder of amorphous magnetically soft alloy needs to be pressed at a temperature lower than the crystallization temperature of the alloy so as to retain the amorphous state. Since the alloy powder can not be bulked at this temperature, it is practice to mix a glass powder of low softening point with the alloy powder and to heat the mixture so as to bond the alloy particles with the glass.
However, if the amount of glass for use as a binder is excessive, the resulting body has impaired magnetic characteristics. The glass is therefore used generally in a small amount, whereas the alloy particles are then more likely to contact with one another to reduce the electric resistance of the pressed body and permit generation of eddy current between the particles, consequently lowering the magnetic permeability in the high frequency range. Further if used in an insufficient amount, the glass fails to satisfactorily bond the alloy particles to result in the drawback of lower mechanical strength.
To avoid the above problem, it is required to thoroughly mix the alloy powder and the glass powder together before pressing so that the glass as softened will uniformly cover the alloy particles during the pressing step.
Conventionally, the alloy powder and the glass powder are mixed together in a mixer, and the mixture is thereafter pressed hot. The mixer affords a substantially uniform mixture, which nevertheless becomes no longer uniform due to the difference in specific gravity when charged into a press die, so that the pressed body obtained includes portions wherein the glass is absent between the alloy particles. This entails the drawback that the alloy particles are not insulated from one another effectively to reduce the magnetic permeability in the high frequency range.
In addition to the pressing process described, the explosive process, impact gun process, etc. are available for bulking the powder of amorphous magnetically soft alloy, whereas these processes not only require a special apparatus for giving very great energy but also have the problem that the shaping step is complex and low in productivity.
In bulking a powder of amorphous magnetically soft alloy by heating at a predetermined temperature and pressing with use of a glass of low softening point as a binder, an object of the present invention is provide a process for producing a pressed powder body of amorphous magnetically soft alloy having high mechanical strength and less diminished in magnetic permeability in the high frequency range by bonding particles of the amorphous magnetically soft alloy to one another with the glass.